The advent of smoke detectors has led to the saving of countless lives each year. The effectiveness and decreasing costs of smoke detectors has resulted in their widespread use. More recently, carbon monoxide detectors have found growing appeal and use in both residential and commercial applications. Carbon monoxide detectors include an active element which is sensitive to carbon monoxide, and like smoke detectors, a loud alarm is activated upon detection of dangerous levels of carbon monoxide.
The trend has been to make smoke and carbon monoxide detectors battery-powered. While there are known line-powered devices, battery-powered devices have the advantage of not being susceptible to electrical supply brown-outs or outages.
The principal drawback with battery-powered detectors is the need to ensure that the batteries have been loaded and that the batteries are sufficiently charged to power the detector.
When a smoke detector is accidently activated, for example from food burning on a stove element, there is a tendency to quickly silence the smoke detector by pulling out the batteries. While such an action is effective to deactivate the detector, there is always the risk that the batteries will not be replaced immediately, and as a result the smoke detector will remain in an inactive state.
More recently, certain regulatory bodies, for example Underwriters Laboratories (UL) in the United States, are requiring that some warning be given when batteries are missing from some types of safety devices such as smoke detectors.
Accordingly, there is a need in the art for a device which can be applied to carbon monoxide, smoke detectors and the like, which provides a visible indication that batteries have not been installed in the detector and which also can prevent the detector from being mounted in position without batteries installed.